[Factors associated with the development of atopy in young adults]

To determine the risk factors for the development of atopy in Spanish young adults.

Case-control study over prevalent cases. Carried out in general population between the ages of 20 to 44 years old. Spanish participants of the ECRHS, a random representative sample of Spanish young adults (n = 16,884), and a 20% randomised subsample made by those who answered to a short respiratory questionnaire and had atopy assessed, was studied. Atopy was defined as having serum specific IgE positivity to the following aeroallergnes: cat dander, Cladosporium herbarum, Dermatophagoides pteronyssinus, Parietaria judaica and Phleum pratense.

Several factors had a statistically significant effect. In addition to male gender and lower age, maternal allergy (OR = 1.63; 95% CI = 1.11-2.40), having allergic siblings (OR = 1.40; 95% CI = 1.06-1.90) and a higher educational level (OR = 1.69; 95% CI = 1.22-2.34) were associated with the presence of high levels of specific IgE in our sample. Moreover, having had older siblings, especially older brothers appears to be a protective factor to the development of atopy but not in a statistically significant way, while having had pet birds during childhood appears to enhance the risk.

In addition to the familial variables that indicates both environmental and genetic factors, educational level seems to have low degree of association with atopy; this feature shows that variables related with life style are involved in atopy development.